Oxidative Alkane C−H Alkoxycarbonylation

Abstract

Directly utilizing a chemical feedstock to construct valuable compounds is an attractive prospect in organic synthesis. In particular, the combination of C(sp(3) )-H activation and oxidative carbonylation involving alkanes and CO gas is a promising and efficient method to synthesize carbonyl derivatives. However, due to the high C-H bond dissociation energy and low polarity of unactivated alkanes, the carbonylation of unactivated C(sp(3) )-H bonds still remains a great challenge. In this work, we introduce a palladium-catalyzed radical oxidative alkoxycarbonylation of alkanes to prepare numerous alkyl carboxylates. Various alkanes and alcohols were compatible, generating the desired products in up to 94 % yield. Remarkably, ethane, a constituent of natural gas, could be employed as a substrate under the standard reaction conditions. Preliminary mechanistic studies revealed a probable palladium-catalyzed radical process.

Influence of annealing temperature on the phase transformation of Al2O3

“…This will be further confirmed using the FESEM micrographs. It is worth to mention that the highly crystalline of -Al2O3 can be formed at 1000 °C, it is lower than the reported temperatures using similar combustion agent of citric acid [1,14,18]. The FESEM micrographs of the synthesized Al2O3 are given in Figure 2.…”

“…At temperature range of 500 °C and 700 °C, the -Al2O3 material was formed [5,6], the annealing at 750 °C exhibited the Al2O3 [7], and the Al2O3 were formed between 900 °C and 1000 °C [6,8]. The stable -Al2O3 can be formed at 1100 °C and above [1,5,9].…”

“…It has been used in many applications such as coatings [1], catalyst [2], electrical insulator [2,4], etc. These various applications were attributable to different phases of Al2O3.…”

“…There are various methods have been reported to produce Al2O3 powders such as sol-gel [10,11], hydrothermal [12], co-precipitation [13] mechanical milling [1] and combustion [14,15]. The combustion method is a promising technique to synthesize pure Al2O3 materials due to its simplicity, fast and environmental benign.…”

Investigating the Mechanism of Palladium‐Catalyzed Radical Oxidative C(sp3)−H Carbonylation: A DFT Study

“…Recently,L ei et al reported as imple and efficient method for constructing alkyl esters from simple alkanesa nd alcohols (Scheme 1), whichp rovides an ovel radical process for ester synthesis. [19] However,t he detailed mechanism of this radical carbonylation reaction, asw ell as as eries of radical-radical coupling reactions, still remains unclear. [20] As eries of radical generationsa nd conversions occur in this pathway.H owever, the capture, stabilization, and release of radicali ntermediates by transition-metal catalysts have been seldom investigated in other reports.…”